increase the opening speed.
The lower opening accesses the SA needle valve for ad-
justing the CLOSING speed for unloading the compressor.
The same adjustment applies clockwise to decrease
closing, counterclockwise to increase vane closing.
The vanes are factory set so that from fully closed to fully
open positioning of the vanes requires about 3 minutes and
about 1 minute from fully open to fully closed. (Exception:
CE126 settings are 9 minutes to open and 3 minutes to close).
LOAD RECYCLING THERMOSTAT SETTING
During the initial startup procedure the McQuay Service
technician will set the LRT to control the compressor on and
off line at the proper temperature.
Normally this control should stop the compressor when the
leaving chilled water drops about 3°F below the control point,
but in no case lower than 38°F. For example, if the control
module is set to control at
45”,
the LRT should stop the com-
pressor at 42°F. The LRT has a non-adjustable differential
of
21/z°F
+_
1; therefore, in the example above, compressor
starting would occur at 42”
+
differential.
Since the LRT scale is not highly accurate, a practical set-
ting can be made with the machine running. Turn the dial
clockwise (to a higher temperature) until the compressor
stops. At this point compare the actual water temperature with
the dial setting. If they agree, then reset to the proper cutout
setting
(3” below control point). If they differ, note the dif-
ference and direction and make the setting accordingly.
LOW OIL TEMPERATURE THERMOSTAT
It is important to understand that this thermostat simply
prevents the compressor from starting with cold oil and has
no function after the compressor is started. It is shunted out
at the end of the prelube cycle.
Therefore, the setting needs to be as high as practical
without causing a nuisance. It is normally set about 40°F
above the normal high ambient temperature in the equipment
room. The operator making a setting of the LOT should,
however, consider the range of ambient temperature.
Checking the LOT calibration can be accomplished by ad-
justing the control with the compressor off. Adjust dial
clockwise (to higher temperature) until LOT switch clicks and
then compare the actual oil temperature with the dial reading.
If they differ, note the difference and make setting
accordingly.
IM 307
/
Page 19
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